Thermal transfer printing using a sublimable dye is a method wherein a thermal ink film is heaped on an image receive sheet having a printing layer and heated by a thermal head to print images directly onto the printing layer on the image receive sheet. This method is required to use the image receive sheet on which the printing layer is formed and it is impossible to directly print on any substrate.
In order to print on any substrate, such as plain paper, by using a sublimable dye, it is proposed to use a so-called tack sheet which is composed of a substrate, a releasing layer on the substrate, an adhesive layer on the releasing layer and a printing layer on the adhesive layer. Firstly, printing is conducted on the printing layer on the tack sheet from the color ink film and then the printing layer is peeled by hand from the releasing layer and adhered on any substrates through the adhesive layer. Another method using a color ink film on which both a color ink layer and a printing layer are present is also proposed. In this method, the printing layer is transferred onto a plain paper and then the color ink layer is heaped on the printing layer, followed by printing thereon (see Japanese Kokai Publication 2-63892). It, however, is difficult to conduct the tack sheet method mechanically, because of its tackiness. Also, the tack sheet is essentially used and this makes the process complicated and increases cost. The latter method reduces dot reproducibility because of uneveness of plain paper and ununiformity of cellulose fibers.